Báo cáo khoa học: Mating system in a clonal Douglas fir (Pseudotsuga menziesii (Mirb) Franco) seed orchard. I. Gene diversity and structure

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Báo cáo khoa học: " Mating system in a clonal Douglas fir (Pseudotsuga menziesii (Mirb) Franco) seed orchard. I. Gene diversity and structure" article Original Mating system in a clonal Douglas fir (Pseudotsuga menziesii (Mirb) Franco) seed orchard. I. Gene diversity and structure T D Prat Caquelard Laboratoire INRA-ENGREF de sciences forestières, 14, Girardet, 54042 Nancy cedex, France rue 15 (Received 15 February 1994; accepted July 1994)Summary — The clonal seed orchard studied consisted of 60 clones phenotypically selected in Dou-glas fir stands planted in France during the first half of the twentieth century. The genotype of every clonewas characterised using isozyme techniques. Seven enzyme systems were studied, 1 was mono-morphic, and 9 polymorphic loci were analysed. Seven loci (from 5 enzyme systems) were sufficientfor genetic identification of each clone. Rare alleles were noticed at 7 of the 9 polymorphic loci studied.Three rare alleles were used to assess the selfing rate of individual ramets, but 2 of them might haveled to erroneous results because of their selective disadvantage. The individual selfing rates, assessedfrom the rare allele transmission by pollen, were low (2-5%). The gene diversity in pollen received bya single ramet was not representative of that of the seed orchard, and was not similar to that expectedaccording to the seed orchard composition. Commercial seed crop exhibited a higher fixation index thanthat related to selfing rate and a significant deviation from the allelic frequencies expected in theorchard.isozyme/ mating system / rare allele / selfing Pseudotsuga menziesii= Douglas fir /Résumé — Régime de reproduction dans un verger à graines de Douglas (Pseudotsuga men-ziesii (Mirb) Franco). I. Structure et variabilité génétique. Le vergerà graines étudié est constituéde 60 clones sélectionnés phénotypiquement dans des peuplements français de Douglas plantés aucours de la première moitié du XX siècle. Chaque clone a été caractérisé par son profil enzymatique. eSept systèmes enzymatiques ont été révélés, un seul s’est montré monomorphe, 9 locus polymorphesont été analysés. Sept locus (cinq systèmes enzymatiques) étaient suffisants pour l’identification de tousles clones. Sept des 9 locus polymorphes analysés présentaient des allèles rares (portés par un seulclone). Trois allèles rares ont été utilisés pour estimer le taux d’autofécondation individuel de 3 ramets,mais 2 d’entre eux pouvaient fournir des valeurs erronées du fait de leur désavantage sélectif. Les tauxindividuels d’autofécondation observés sont faibles (2 à 5%). La variabilité génétique du nuage polli- INRA, station d’amélioration des arbres forestiers, Ardon, 45160 Olivet, France* Present address:nique reçu par un ramet n’est pas représentative du verger à graines. La semence commerciale du ver-ger montre un indice de fixation supérieur à celui dû à ces taux d’autofécondation, et de plus desécarts significatifs ont été notés dans les fréquences alléliques observées par rapport à celles atten-dues dans le verger compte tenu de sa composition.allèle rare/autofécondation/isoenzyme/Pseudotsuga menziesii = Douglas/régime de repro-ductionINTRODUCTION pollination, is influenced by floral phenol- ogy and pollination distance (Erickson and other factors such well Adams, 1989) as asDouglas fir (Pseudotsuga menziesii (Mirb) pollen availability or fecundity, and indi- asFranco) was introduced into Europe during vidual tree genetic load.the last century. It is favoured by foresters for The purpose of this paper is to describeits growth and high wood quality and has the mating system, and especially to ...